feat: Add GitHub Actions workflow for license checking

Author: billnapier

.github/workflows/license-check.yml

@@ -0,0 +1,58 @@
+name: Check License
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  license-check:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v3
+
+      - name: Find license file
+        id: find_license
+        run: |
+          if [[ -f "LICENSE" ]]; then
+            echo "filename=LICENSE" >> $GITHUB_OUTPUT
+          elif [[ -f "LICENSE.md" ]]; then
+            echo "filename=LICENSE.md" >> $GITHUB_OUTPUT
+          elif [[ -f "LICENSE.txt" ]]; then
+            echo "filename=LICENSE.txt" >> $GITHUB_OUTPUT
+          elif [[ -f "COPYING" ]]; then
+            echo "filename=COPYING" >> $GITHUB_OUTPUT
+          else
+            echo "::error::No license file found. Checked for LICENSE, LICENSE.md, LICENSE.txt, COPYING."
+            exit 1
+          fi
+
+      # The reusable workflow is in a different repository, so we check it out.
+      # Assuming 'billnapier/licenseclassifier' is the repository on GitHub.
+      - name: Check out licenseclassifier repository
+        uses: actions/checkout@v3
+        with:
+          repository: billnapier/licenseclassifier
+          path: ./.licenseclassifier
+
+      - name: Run license classifier
+        id: classify
+        uses: ./.licenseclassifier/.github/workflows/classify.yml
+        with:
+          file_to_classify: ${{ steps.find_license.outputs.filename }}
+
+      - name: Verify license
+        run: |
+          license_name="${{ steps.classify.outputs.license_name }}"
+          echo "Detected license: $license_name"
+          # The prompt mentioned "Apahche", which is likely a typo for "Apache".
+          if [[ "$license_name" == "Apache" || "$license_name" == "MIT" || "$license_name" == "BSD" ]]; then
+            echo "License is compliant."
+          else
+            echo "::error::License '$license_name' is not one of the allowed licenses (Apache, MIT, BSD)."
+            exit 1
+          fi